J.P. Rushton’s theory of ethnic nepotism [pdf] – “Ethnic nepotism due to similarity is a weak social force compared to social identity. However its pervasiveness makes it a potential driver of evolutionary and social change, a potential borne out by sociological studies of the impact of ethnic diversity on social cohesion and public altruism. Genomics confirms the theory for interactions within populations with sufficient genetic diversity, such as ethnically mixed societies. GST [genetic similarity theory] applied to ethnicity is promising for further research in evolutionary social science because it unifies evolutionary and behavioral mechanisms in a single theory.” – from salter and harpending. h/t hbd bibliography!